Brown Butter Swiss Meringue Buttercream

This brown butter Swiss meringue buttercream is so delicious. It’s light and fluffy with toasty flavor and notes of caramel from the brown butter.

Brown butter frosting is a great way to bring caramel flavor to cakes and cupcakes. This is a Swiss meringue brown butter buttercream frosting so it’s less sweet than an American buttercream recipe.

It means you can lavishly pipe it onto baked goods and it’s not cloyingly sweet!

Swiss meringue buttercream

Swiss meringue buttercream (SMBC) is made by gently cooking egg whites and sugar in a double boiler until the sugar has melted. The mixture is then whipped into a stiff meringue.

Next, lots of room temperature butter is whisked into the meringue, a little at a time, until the mixture comes together into a cloud of delicious frosting. 

What is brown butter?

This browned butter frosting has incredible flavor because of the brown butter. Brown butter, also known as beurre noisette is simply butter that has melted, and then cooked a step further so that the milk solids in the butter caramelize. 

This gives a wonderful caramel nutty flavor to the butter. It’s amazing when added to cookies, cakes and bars too!

How to brown butter

Melt butter over medium heat in a small saucepan. Avoid using a dark pan as you will struggle to see the caramelization of the butter at the bottom of the pan and run the risk of burning it.

Once the butter has melted, let it cook further for around 3-4 minutes, stirring occasionally until the milk solids in the butter have caramelized into a golden amber color and the butter smells nutty.

When you later use this butter, ensure you use all those deep golden brown bits that accumulate at the bottom of the saucepan. They have all the flavor.

Ingredients

This buttercream is made with basic ingredients. You’ll find all the ingredient amounts for this brown butter frosting in the printable recipe card at the end of this post. This is just a rundown of the ingredients. You will need –

• Egg whites (from large eggs). You can use the leftover yolks in these chocolate chip egg yolk cookies
• Granulated sugar. You can also use soft brown sugar for a deeper caramel flavor. (Not powdered sugar)
• Unsalted butter at room temperature- Divided. Some will be browned and some will be left as is.
• Vanilla extract or paste
• Salt

Equipment

You will need a stand mixer to make the brown butter meringue buttercream, one with a whisk attachment and a paddle attachment. You will also need a heatproof bowl to cook the egg whites in. I use the metal bowl of my stand mixer to do this.

Method

Butter

Firstly, prepare the brown butter for the frosting as this needs time to cool. Over medium heat, melt 113g of the butter (1/2 cup butter.) Avoid using a dark pan as you will struggle to see the caramelization of the butter and run the risk of burning it.

Once you have melted butter, let it cook further for around 3 minutes, stirring occasionally until the milk solids in the butter have caramelized into a golden amber color and the butter smells nutty.

Pour butter into a flat dish. Ensure you get all the browned bits as that’s where the flavor is. Refrigerate it until it has just solidified (but not so cold that it’s rock hard).

Egg whites

Bring a pot of water (with 1 inch of water) to a simmer. 

In the metal bowl of a stand mixer, or other heatproof bowl, add egg whites and granulated sugar. Balance the bowl over this simmering water bath. Ensure the bottom of the bowl isn’t touching the water. Whisk continuously as the egg whites warm up and keep whisking until all the sugar has dissolved or the temperature reads 160°F (71°C) on an instant-thermometer. Don’t stop stirring or some egg whites may overcook on the edges of the bowl. 

Once the sugar has dissolved, place the bowl in your stand mixer fitted with the whisk attachment.

Beat on medium-high speed until a meringue with stiff peaks forms and the meringue has cooled down to room temperature. When you touch the sides of the bowl they shouldn’t feel warm. With the mixer on medium-high speed, feed in the solidified brown butter.

Add in the remaining butter, a cube at a time. Allow the butter to incorporate fully before adding the next cube.

At this point, the frosting can suddenly appear split or curdled and look like cottage cheese. Just keep beating the mixture until it comes together into a thick and cohesive buttercream. This can take a lot of beating so don’t give up if it doesn’t seem to come together – it will. Keep beating it until it no longer looks greasy.

Once the mixture is thick and cohesive, beat in the vanilla and salt and beat until thick and fluffy.

Switch to the paddle attachment and beat on low for 10 minutes to remove the larger air bubbles in the buttercream.

Frosting tips

• Ensure your bowl is clean when adding the egg whites and that no yolk gets into the mixture as this can stop you from achieving stiff peaks.
• Avoid making this buttercream on hot days. If you really need to, make it in the morning when temperatures aren’t too warm yet.
• Keep whisking the egg whites as they cook over the hot water so you don’t scramble any egg whites!
• Make sure both your butter and meringue are at room temperature before beating in the butter. Room temperature butter should leave a slight indent when pressed but not be so warm that it’s greasy and melty.

Serving

This recipe makes around 4 1/2 cups of frosting which is enough to generously frost a double-layer 9-inch cake or a 3-layer 8-inch cake.

It could frost a 3-layer 9-inch cake too depending on how much frosting you use on the cake. It can also frost 24 cupcakes.

A smaller version of this frosting is used in this mini vanilla cake recipe.

Storing

Store the brown butter Swiss meringue buttercream in a covered bowl at room temperature for 1-2 days, as long as the room doesn’t get too warm.

Store it in the fridge or freezer if your kitchen is hot until needed. If stored in a cold place it will need to be whipped again before piping.

Rewhipping cold SMBC

As the buttercream cools in the refrigerator, it will become hard as all the butter in there has solidified. Bring it back to room temperature and whip it to make it creamy again.

You can leave it to sit out and warm up for a few hours, or you can gently warm the bowl of buttercream over a hot water bath until the buttercream edges in the bowl begin to melt.

Once the edges have melted, place the bowl back in the stand mixer and whip it for 3-5 minutes until creamy again. If the mixture appears to split and become curdled, the butter is still too cold and it will need a little more warming.

If it becomes soupy and liquid it has warmed too much, so place it back in the fridge to cool it down. Whichever way it swings, there’s a fix for it, you just need to get it at the right temperature. 

How to use this brown butter icing recipe

Brown butter frosting pairs really well with –

• Carrot cake
• Banana cake or banana cupcakes
• Vanilla cake or vanilla cupcakes
• Chocolate caramel cupcakes

For another not-too-sweet frosting recipe, try this Ermine frosting.

The Different Types of Meringue